ELECTRICALLY-INDUCED MORPHOLOGICAL INSTABILITIES IN FREE DENDRITE GROWTH

We describe a new instability mechanism in free dendrite growth, which arises from electrically enhanced diffusion of polar molecules near t he dendrite tip. For a small applied potential, the dendrite tip veloc ity increases slowly with potential, as is described by an extension o f normal solvability theory. Above a threshold potential, however, cap illarity is insufficient to stabilize growth. We present observations that confirm this instability, which brings about a transition from en hanced normal dendrite growth to a rapidly growing needle morphology w ith strongly suppressed sidebranching.